A truly wonderful book that I am reading for the third time. Much superior (in my opinion) to The Lord Of The Rings, it chronicles the creation of the universe through to the voyage of Eärendil at the end of the annals of the First Age.
Several other writups here complain that the Silmarillion is too boring, fussy, or biblical-sounding, and that is what I found when I first read it (when I was nine), but I find that this sort of writing seems more 'mythical' and is generally much more enjoyable than the usual sort of fantasy writing.
But the real reason for my interest in the Silmarillion is that I am a conlanger and the Silmarillion was created as a medium for Tolkien's conlanging, which, among other things produced Quenya, which I (and many others - the best website for Tolkien's languages is www.uib.no/People/hnohf) think is the most aesthetically pleasing conlang I have ever seen, and every name in the Silmarillion (as is also the case for The Lord Of The Rings) has a meaning.
This is definetly a cool book.

"On my father's death it fell to me to try to bring the work into publishable form. It became clear to me that to attempt to present, within the covers of a single book, the diversity of the materials -- to show The Silmarillion as in truth a continuing and evolving creation extending over more than half a century -- would in fact lead to confusion and the submerging of what is essential.

Upon occasion, a scholar finds that the organization and presentation of another person's life work becoming his or her own life's work, and a fulfilling one at that. After the death of J.R.R. Tolkien in 1973, his son Christopher Tolkien was left with a collection of fragmentary stories and notes about the mythology underyling The Hobbit and The Lord of the Rings. Since this mythology was built up over its creator's entire lifetime, built like a painting in layers which were often covered up by later layers, the task was certainly daunting. But the younger Tolkien, with the assistance of Guy Gavriel Kay, began to go through his father's half-finished manuscripts, notes, and scribblings, to put something together that could be presented to the world. The Silmarillion, published in 1977, was the admirable result.

Ainulindalë is the theology behind the creation of Arda, the pattern set by the Ainur and its realization by Ilúvatar; Valaquenta is a list of the Ainur who entered Arda, the Powers of the Earth, or Valar.

The central work, Quenta Silmarillion, is itself more a collection of sagas than a single narrative. It begins as an æteological work, telling of how the works and struggles of the Valar shaped Arda, and continues with the appearance of the Eldar and their journey to Valinor. It then moves into the story of Fëanor and the Silmarils, their theft by Melkor, the revolt of the Noldor, and their return to Middle-Earth.

The last two sections connect the events of the First Age to the time of the Lord of the Rings along two parallel tracks. All of the information in Of the Rings of Power and the Third Age will be recognizable if you have read LotR carefully enough.

The Silmarillion's fragmentary nature is a strength rather than a drawback. It works to convince us that this is a realmythology built from stories collected over millennia rather than something made up on the spot for money. After all, this is exactly what it is!

After the release of The Silmarillion, Christopher Tolkien embarked upon the presentation of the rest of his father's notes, possible other ways he might have put the story together. The publisher, Houghton Mifflin, has packaged as these as "The History of Middle-Earth", containing early versions of the mythology abandoned by the elder Tolkien, as well as buried layers of the story. While interesting in their own right, these latter works frequently come off as broad brush strokes better left covered by the artist. Regardless of individual merit, however, all of them draw their strength from the Silmarillion and you will always find youself comparing them to it. If nothing else, they show the excellent work done by Kay and the younger Tolkien, showing that he really made the best choices while pulling together the original publication.